This invention relates to filter assemblies and to connectors and systems including filter assemblies.
The invention is more particularly concerned with filtered connectors, couplings, feedthroughs or the like.
Filtered connectors are used to reduce high frequency interference signals on electrical paths through the connector. The connectors are often used to make connection to electrical apparatus within a housing, so as to minimize the amount of external electrical interference that passes along the electrical path into the housing and to minimize the amount of interference generated within the housing that is transmitted externally of the housing. The construction of filtered connectors usually comprises an external metal shell secured to the housing and adapted to mate with a shell of a cooperating connector. A filter element is connected between the shell and each contact or wire within the filtered connector. The filter element acts as a shunt path for high frequency signals on the contact or wire so that these pass to ground via the shell. The filter element may be a single component or a combination of components such as capacitors and ferrite inductors. The filter element may be a simple capacitive filter, a PI filter, a T filter or a combination of these. It may also be necessary for the connector to include a transient voltage suppressor to reduce the effect of lightning strikes. An example of a filtered connector is described in GB 2233511A.
In some applications, the connector may have a large number of contacts each of which has to be filtered. Because space within the connectors is limited, the size of the filter assembly that can be used is also limited. This creates a particular problem with contacts or lines in the connector required to carry a high dc voltage, because capacitors with a high capacitance and capable of handling a high voltage have a large size. In order to reduce the size sufficiently for the capacitors to be incorporated in a connector, it is usual to use capacitors with a lower capacitance. This has the disadvantage that it reduces the effectiveness of the filtering.